Friction Drive Disc Spoke Repair

[Dave Neuhaus]

1913 Metz with friction drive

 

Explanation of the friction drive that you need to know to understand this post:  The drive disc is attached to the back of the engine and spins with the engine.  The driven wheel can be positioned anywhere against the drive disc giving it a (theoretically, but not really) infinite ratio.  Moving it just past center is reverse.  Where other cars have a clutch the Metz has a pedal that brings the driven wheel against the drive disc.  The pedal gets locked down to maintain pressure when driving.  My car's drive disc uses a 1/4" thick aluminum disc that is supported by 12 wood spokes.

 

I replaced the drive-disc spoke bolts and discovered that the wood spokes were all skewed.  Only 1 was square, while the rest were bent forward in varying amounts, some as much as 0.150".

 

I found a quick and easy way to repair them.  I used JB-Weld to fill in the gaps to return the original spoke to square.  Squareness was achieved by using a flat and straight hunk of wood.  I added a spacer to make it just fit between the "driven-shaft" and the drive-disk.  I taped wax paper to the wood to prevent the JB-Weld from sticking to my jig.  The spoke surfaces were prepped by sanding and gouges from a file were used to give the surface some teeth.

 

After applying the JB-Weld I dropped my jig in place and applied the drive foot peddle, locking it in place.  This moves the shaft forward against the jig and squeezes out the excess JB-Weld.  After 30 minutes I can remove the jig.  The wax-paper peals right off.  With the repair not yet fully cured it is easy to trim off the excess with a knife.  

 

There are bolt holes at the ends of the spokes.  I still have to clean them up, but it won't be bad because I filled them with modeling clay before I started. 

 

I am not quite done with the process yet.  I may find that some are not yet square.  If that's the case its a simple matter to repeat the process or even sand down some spokes if needed.  The worst case scenario would be if I created an imbalance producing a vibration.  The worst spokes are not all in the same area, so hopefully it will be ok.

 

 

[Luv2Wrench]

Great job!  Mine was in slightly worse condition and required a complete rebuild.  I also machined new bolts and repaired the three pieces that make up the metal center section.  Should be done with it next week.

 

[Dave Neuhaus]

Wow, that was pretty far gone.  That is a great transformation.

[Dave Neuhaus]

After completing the JB weld repair I numbered the spokes and removed them.  Then I weighed them with a postal scale.

I thought the spokes with the most JB weld would be the heaviest, but the opposite was true!

I think that is because the heavy and dense spokes held the correct shape and the soft and light spokes did more bending.

 

I made some thicker washers to use on the bolts of the lightest spokes.  It's not perfect, but better than it was.